Roldan scored in the 18th minute to ignite the crowd of 51,796, but Darren Mattocks drew a penalty during first-half stoppage time, and Valeri beat goalkeeper Stefan Frei.
Jordan Morris was stuffed on a pair of breakaway attempts inside the first 15 minutes of the second half as Attinella kept the Timbers in the game.
It was a banner day for Roldan who was named to the U.S. squad for upcoming World Cup qualifying earlier on Sunday, just the second national team selection for the 22-year-old.
But Portland controlled the latter stages of the first half and Mattocks earned the penalty when he tumbled over Frei while also appearing to be shoved by defender Kelvin Leerdam.
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